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| United States Patent |
5,168,105
|
|
Anderson, Jr.
, et al.
|
December 1, 1992
|
Metallic water borne base coat composition based on acrylic latex resins
using an acrylic resin having acid and nonionic functionality for
aluminum storage and a treated hetorite clay for rheology control-water
base 5
Abstract
There is disclosed a metallic and nonmetallic water borne base coat
compositions exhibiting excellent appearance. A method for long term
stability and the introduction of aluminum flake pigments into a water
borne coating is also disclosed. The method is based on storing the
aluminum flake in a solvent environment with introduction of the aluminum
flake in to the aqueous environment just before appling the base coat
coating. A water reducible acrylic resin with nonionic and acid
functionality has been disclosed that allows for direct introduction of
aluminum flake in to an aqueous environment. The coating vehicle is based
on acrylic latex vehicle which exhibits excellent drying and film
properties. The rheology control agent employed allows for a wetter
application of the coating to the substrate. The coating compositions
disclosed are also in compliance with current and proposed volatile
organic compound regulations.
| Inventors:
|
Anderson, Jr.; James L. (Grand Rapids, OH);
Finkenauer; Horst J. (Waterville, OH);
Newton; David L. (Toledo, OH);
Jones; Jeff P. (Toledo, OH)
|
| Assignee:
|
BASF Corporation (Parsippany, NJ)
|
| Appl. No.:
|
553100 |
| Filed:
|
September 10, 1990 |
| Current U.S. Class: |
524/441; 524/446; 524/522; 524/523; 524/558 |
| Intern'l Class: |
C08J 003/00; C08K 003/08; C08K 003/34; C08L 033/00 |
| Field of Search: |
524/441,558,522,523,446
|
References Cited
U.S. Patent Documents
| T102301 | Oct., 1982 | Walker | 524/556.
|
| 3862071 | Jan., 1973 | Di Carlo | 524/437.
|
| 4243565 | Jan., 1981 | Nishino et al. | 524/441.
|
| 4384096 | May., 1983 | Sonnabend | 524/558.
|
| 4490499 | Dec., 1984 | Huybrechts | 524/441.
|
| 4735995 | Apr., 1988 | Chettiath | 524/529.
|
| 4764554 | Aug., 1988 | Tonge | 524/558.
|
Primary Examiner: Michl; Paul R.
Assistant Examiner: Niland; Patrick
Attorney, Agent or Firm: Chipaloski; Michael R.
Claims
We claim:
1. A method of forming a water-borne metallic base coat kit composition
consisting essentially of mixing:
a) an aluminum base consisting essentially of
1. one or more pigments selected from the group consisting of metallic and
metallic effect pigments in a water reducible solvent borne acrylic resin
having nonionic and acid functionality resulting from the solution
polymerization of ethylenically unsaturated monomers wherein at least two
ethylenically unsaturated monomers are acid and poly(ethylene oxide)
functional and optionally ethylenically unsaturated monomer containing
hydroxyl groups to give a polymer with a glass transition temperature from
about -20 to 50 C. (using the Fox method of Tg calculation), relative
weight average molecular weight of 100 to 50,000, an acid number of 5 to
50, a hydroxyl number of 0-50, and a final poly- (ethylene oxide) level of
1) -50% by weight,
2) a solvent borne aluminum flake at a level of 4-30% by weight,
3) 25-55% total solids by weight,
4) 35-50% total water miscible organic solvent by weight,
5) 5-35% total binder weight.
b) an aqueous pigmented base consisting essentially of an acrylic latex
resin and,
c) an aqueous reducer base containing a sodium magnesium silicate hectorite
clay treated with polypropylene glycol as a rheology control agent.
2. A method of forming a water-borne metallic base coat kit composition
consisting essentially of mixing:
a) an aluminum base consisting essentially of:
1. one or more pigments selected from the group consisting of metallic and
metallic effect pigments in a water reducible solvent borne acrylic resin
having nonionic and acid functionality resulting from the solution
polymerization of ethylenically unsaturated monomers wherein at least two
ethylenically unsaturated monomers are acid and poly(ethylene oxide)
functional and optionally ethylenically unsaturated monomer containing
hydroxyl groups to give a polymer with a glass transition temperature from
about -20 to 50 C. (using the Fox method of Tg calculation), relative
weight average molecular weight of 100 to 50,000, an acid number of 5 to
50, a hydroxyl number of 0-50, and a final poly(ethylene oxide) level of
1-50% by weight,
2. an aluminum flake treated for water stability at a level of 4-30% by
weight,
3. 25-55% total solids by weight,
4. 35-50% total water miscible organic solvent by weight,
5. 5-35% total binder by weight,
b) an aqueous pigmented base consisting essentially of an acrylic latex
resin and,
c) an aqueous reducer base containing a sodium lithium magnesium silicate
hectorite clay treated with polypropylene glycol as a rheology control
agent.
Description
FIELD OF INVENTION
The present invention is concerned with a water borne coating composition
designed for the coating of transportation vehicles. The invention is
related to coating compositions primarily for a base coat of a multi-coat
system which includes primers and transparent clear coats, particularly
with base coats containing metallic pigments, based on acrylic latex
polymers
BACKGROUND AND PRIOR ART
Related automotive paint compositions of this type are disclosed in U.S.
patent applications titled METALLIC WATER BORNE BASE COAT COMPOSITION
BASED ON ACRYLIC LATEX RESINS USING A WATER REDUCIBLE RESIN FOR ALUMINUM
STORAGE AND A PREGELLED HECTRORITE CLAY FOR RHEOLOGY CONTROL Ser. No.
07/553,065 filed Sep. 10, 1990, METALLIC WATER BORNE BASE COAT COMPOSITION
BASED ON ACRYLIC LATEX RESINS USING A WATER REDUCIBLE RESIN FOR ALUMINUM
STORAGE AND A TREATED HECTORITE CLAY FOR RHEOLOGY CONTROL Ser. No.
07/553,063 filed Jul. 13, 1990, METALLIC WATER BORNE BASE COAT COMPOSITION
BASED ON ACRYLIC LATEX RESINS USING AN ACRYLIC RESIN HAVING ACID AND
NONIONIC FUNCTIONALITY FOR ALUMINUM STORAGE AND A PREGELLED HETORITE CLAY
FOR RHEOLOGY CONTROL Ser. No. 07/554,606 filed Sep. 10, 1990, METALLIC
WATER BORNE BASE COAT COMPOSITION BASED ON ACRYLIC LATEX RESINS AND
ACRYLIC RESINS DERIVED FROM ACRYLIC MONOMERS HAVING NONIONIC, URETHANE AND
ACID FUNCTIONALITY FOR ALUMINUM STORAGE AND A PREGELLED HECTORITE CLAY FOR
RHEOLOGY CONTROL Ser. No. 07/553,069 filed Sep. 10, 1990, METALLIC WATER
BORNE BASE COAT COMPOSITION BASED ON ACRYLIC LATEX RESINS AND ACRYLIC
RESINS DERIVED FROM ACRYLIC MONOMERS HAVING NONIONIC, URETHANE AND ACID
FUNCTIONALITY FOR ALUMINUM STORAGE AND A TREATED HECTORITE CLAY FOR
RHEOLOGY CONTROL Ser. No. 07/553,070 filed Jul. 13, 1990, METALLIC WATER
BORNE BASE COAT COMPOSITON BASED ON ACRYLIC LATEX RESINS USING ACRYLIC
RESINS DERIVED FROM VINYL MONOMERS HAVING NONIONIC AND URETHANE
FUNCTIONALITY FOR ALUMINUM STORAGE AND A PREGELLED HECTORITE CLAY FOR
RHEOLOGY CONTROL Ser. No. 07/553,066 filed Jul. 13, 1990, METALLIC WATER
BORNE BASE COAT COMPOSITON BASED ON ACRYLIC LATEX RESINS USING ACRYLIC
RESINS DERIVED FROM VINYL MONOMERS HAVING NONIONIC AND URETHANE
FUNCTIONALITY FOR ALUMINUM STORAGE AND A TREATED HECTORITE CLAY FOR
RHEOLOGY CONTROL Ser. No. 07/553,067 filed Jul. 13, 1990, METALLIC WATER
BORNE BASECOAT COMPOSITION BASED ON ACRYLIC LATEX RESINS USING ACRYLIC
RESINS DERIVED FROM GRAFTING AN ISOCYANATE ADDUCT HAVING URETHANE AND
NONIONIC FUNCTIONALITY ON TO AN ACRYLIC RESIN HAVING ACTIVE HYDROGEN
FUNCTIONALITY FOR ALUMINUM STORAGE AND A PREGELLED HECTORITE CLAY FOR
RHEOLOGY CONTROL Ser. No. 07/553,064 filed Sep. 10, 1990, METALLIC WATER
BORNE BASECOAT COMPOSITION BASED ON ACRYLIC LATEX RESINS USING ACRYLIC
RESINS DERIVED FROM GRAFTING AN ISOCYANATE ADDUCT HAVING URETHANE AND
NONIONIC FUNCTIONALITY ON TO AN ACRYLIC RESIN HAVING ACTIVE HYDROGEN
FUNCTIONALITY FOR ALUMINUM STORAGE AND A TREATED HECTORITE CLAY FOR
RHEOLOGY CONTROL Ser. No. 07/553,068 filed Sep. 10, 1990, and ACRYLIC
LATEX METALLIC WATER BORNE BASE COAT OF IMPROVED APPEARANCE Ser. No.
07/355,959 filed May 23, 1989. All of these U.S. patents and applications
are incorporated herein by reference.
It is customary in the painting of an automobile that series of coatings be
applied to the substrate. The first coat being the primer followed by the
base coat and finally the clear coat. The base coat provides the good
decorative quality to the final finish via organic and inorganic pigments.
In many automobile finishes, a metallic finish is desired. To obtain this
metallic effect, metallic pigments are present in the base coat, typically
aluminum flakes. The aluminum flakes in the base coat contribute to the
glossy lustrous appearance of the final finish.
Another feature that aluminum flakes contribute to the appearance of the
final finish is the change of brightness as the viewing angle is changed.
Typically, the final finish is bright when viewed at a 90 degree angle,
however, when the viewing angle is changed to 180 degrees, the coating has
a dark appearance. This phenomenon is known as "flop" in the automotive
field and is highly desired. The ultimate in "flop" is achieved when the
aluminum flakes are orientated parallel to the substrate. Random
orientation of the aluminum flake results in a final finish exhibiting
bright and dark areas when viewed at 90 degrees. This appearance is known
as mottling and detracts from the final appearance of the final finish. In
general, the metal fixation in base coats is achieved by a rheology
modifiers such as inorganic and organic thickeners. The particular
rheology control agent used in this invention results in a non-mottled,
high head-on-brightness, outstanding flop, and high quality finish, even
in the case of a silver metallic base coat. Also, use of this particular
rheology control agent allows the coating to be applied wetter during the
application process.
In the current market place, automobile coatings, especially base coats,
contain a high level of organic solvent. With increasing concern about the
volatile organic emissions into the atmosphere, an intensive effort in
research and development of coatings containing mainly water as the
solvent with a small level of organic solvent is under way. An example of
such an effort is U.S. Pat. No. 4,730,020 which discloses a
water-dilutable coating composition comprising specifically selected
acrylic copolymers, solvent blends, coloring and/or optical effect
pigments and polymer dispersions. To obtain the desired optical effect of
the metallic flakes, the correct combination of acrylic copolymer and
solvent blend must be achieved. An aqueous thermosetting acrylic resin
described by U.S. Pat. No. 3,862,071 controls the metallic pigment
orientation by the addition of a water insoluble copolymer. Microgel
technology as described by GB-PS No. 2,073,609 also results in the proper
metal orientation. Also disclosed in DE No. 3,210,051 is an attempt to
control metallic pigment orientation using polyurethane dispersions.
Cellulosic esters have also been used to control metal fixation as
disclosed in DE No 3,216,549. The rheology modifiers or rheology control
agents for water borne coatings have poor shelve stability, poor
weathering characteristics and are cumbersome to use. The particular
rheology control agent used in this invention results in a non-mottled,
high head-on-brightness, outstanding flop, and high quality finish, even
in the case of a silver metallic base coat and does not suffer from the
problems cited earlier.
The use of acrylic latex resin in a base coat formulation has been
disclosed in European Application 0 287 144 A1, however, this application
does not disclose any rheology control agents, pigment dispersion
procedures, method for aluminum storage and requires that the acrylic
latex resin be prepared in 2 or more steps by emulsion polymerization.
Typically, coating compositions used in the automotive market, especially
in the automotive after market, are produced by mixing various bases to
give the desired color. These coating compositions are then applied in
about 1-5 days after preparation. A major problem is the introduction of
aluminum flakes which react with water to generate hydrogen gas.
Therefore, the aluminum flake must be segregated from the rest of the
water borne components to minimize this hazard. This invention also
describes a method for the storage of aluminum flake in an organic medium
with introduction of the flakes directly into the aqueous environment
without neutralization just prior to application of the coating system.
SUMMARY OF INVENTION
This invention relates to water borne compositions for use in metallic and
nonmetallic base coats in a multicoat system for the automotive market.
The instant invention is concerned with an acrylic latex coating
composition for use in an automotive paint base coat composition.
Typically, a water borne basecoat coating composition for the refinish
market are in a kit form. The invention also relates to base coats
containing pigments, metallic pigments, organic solvents, and conventional
paint additives. The outstanding metal control exhibited by this coating
composition is attributed to the rheology control agent, the film
shrinkage of the acrylic latex vehicle while drying and a wax. The use of
acrylic latex results in a very fast dry time. This coating composition
provides a base coat that satisfies current and proposed volatile organic
compound regulations. Even with conventional non-metallic pigments, the
coating exhibits excellent appearance.
This invention describes a method for the storage of aluminum flake in an
organic medium with introduction of the flakes into the aqueous
environment just prior to application of the coating system. This method
minimizes the potential hazard of the aluminum flake reacting with water
to form hydrogen gas and dulling of the aluminum flake during storage.
This method can also be used for the storage of other water sensitive
pigments such as copper and brass. Other pigments such as plastic films,
mica and coated metallic foils can be stored using this method.
The automotive metallic base coat paint comprises three components; A)
aluminum base, B) pigmented or unpigmented base, and C) reducer base. The
automotive nonmetallic base coat paint comprises two components; A)
pigmented base and B) reducer base. Component A, the aluminum base, is
composed of metallic flakes slurred into a solvent borne acrylic resin and
water miscible solvents. The acrylic resin used in this component has
nonionic and acid functionality allowing for direct introduction of the
component into aqueous acrylic latex resin system. The aluminum dispersion
resin is an acrylic polymer in water-miscible solvent(s), formed by the
free-radical initiated polymerization of ethylenically unsaturated
monomers. A polyether-containing ethylenically unsaturated monomer is
included in the monomer mixture, to give a final poly(ethylene oxide)
level of 1-50% by weight, preferably 5-20% by weight. The number average
molecular weight of the polymer is between 1,000 and 50,000 atomic mass
units, its Glass Transition Temperature (Tg) is between -20.degree. and
+50.degree. C. (calculated by the Fox method), a hydroxyl number of 0-50,
and its acid number is from 5 to 50 milligrams of KOH per gram of resin
solids. The viscosity of the final polymer is 3,000-10,000 cps with a
solids content of 60-70% by weight at 23 C. Commonly used metallic
pigments, used singularly or as a mixture are copper, copper alloys,
aluminum, steel, mica, plastic films, and coated metallic foils,
preferably aluminum at a level of 4-30% by weight, preferably 20-30% by
weight. The aluminum base contains 5-35%, preferably 20-30% by weight of
the solvent borne water reducible acrylic resin. The organic solvent for
this base must be water miscible. Examples of solvents are methanol,
ethanol, propanol, butanol, N-methylpyrrolidone, glycols, glycol ethers,
glycol acetates, diethylene glycol ethers, diethylene glycol acetates,
propylene glycol ethers, propylene glycol acetates, dipropylene glycol
ethers, dipropylene glycol acetates, specially preferred are ethylene
glycol propyl ether, ethylene glycol butyl ether, ethylene glycol hexyl
ether, propylene methyl ether, propylene ethyl ether, propylene propyl
ether, propylene butyl ether, propylene hexyl ether, dipropylene methyl
ether, dipropylene ethyl ether, dipropylene propyl ether, and dipropylene
butyl ether.
Component A, the aluminum base, has a total solids level of 25-55 by
weight, total volatile organic solvent level of 35-50% by weight, total
metallic pigment level of 4-30% by weight and total binder level of 5-35%
by weight.
By binder we mean the nonvolatile portion of the resinous vehicle of a
coating, in particular reference is given to Paint & Coatings Dictonary,
Published by The Federation of Societies for Coatings Technology, 1978. By
solids we mean the nonvolatile matter in a coating composition left behind
after drying, in particular reference is given to Paint & Coatings
Dectonary, Published by the Federation of Societies for Coatings
Technology, 1978.
Component B, pigmented base, contains acrylic latex grinding polymer and
acrylic latex film forming vehicle at a level of 5-50%, preferably 15-50%.
This level depends on the pigment in the component. The level of pigment
in component B is 0.5-35% by weight, this level depends on the pigment
characteristics also. Typically, a pigment to binder weight ratio of about
10/100 to 300/100 is acceptable. The pigments are typically ground using
conventional dispersion equipment such as sand mills, pearl mills, ball
mills, horizonal mills, and vertical mills. Optional wetting agents,
surfactants, and dispersing aids can be employed. This component may also
contain a wax composed of ethylene and/or ethylenically unsaturated
monomers alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, 2-propyl (meth)acrylate, butyl
(meth)acrylate, 2-butyl(meth)acrylate, 2-methylpropyl (meth)acrylate,
t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl
(meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl
(meth)acrylate, stearyl (meth)acrylate, dicyclopentadienyl (meth)acrylate,
and isobornyl (meth)acrylate; aryl monomers such as styrene, alpha-methyl
styrene, vinyl toluene, t-butyl styrene, benzyl (meth)acrylate, and
2-benzylethyl (meth)acrylate; hydroxy monomers such as hydroxyethyl
(meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate,
sec-hydroxybutyl (meth)acrylate, and hydroxyoctyl (meth)acrylate; acid
functional monomers such as acrylic acid, methacrylic acid, maleic acid,
and itaconic acid. Typically, the particle size of the wax particle in the
final dispersion is 0.5 microns to 50 microns, preferably 1.0 to 20.0
microns. The wax is dispersed by conventional techniques or emulsified in
to the resin system to the desired particle size. The proper amount of the
wax dispersion is then added to the pigmented base. The pH of the
pigmented base can be adjusted using ammonia or any water soluble primary
amines, secondary amines, tertiary amines, polyamines and hydroxyamines,
such as ethanolamine, diethanolamine, triethanolamine, n-methylethanol
amine, N,N diethylethanolamine, N-aminoethanolamine,
N-methyldiethanolamine, monoisopropanolamine, diisopropanolamine,
triisopropanolamine, hydroxyamine, butanolamine, hexanolamine, methyl
diethanolamine, N,N-diethylaminoethylamine, ethylene diamine, diethylene
triamine, diethylene tetraamine, hexamethylene tetramine, triethylamine
and the like. The prefered base is ammonia. This component may also
contain a water dipersible polyurethane resin at a level of 0-25% by
weight.
Component B, the pigmented base, has a total solids level of 5-60% by
weight, a total pigment level of 0.0-45% by weight, a total organic
solvent level of 0-25% by weight, a total binder of 20-60% by weight, a
total wax level of 0-20% by weight, a total water level of 40 95% by
weight, a pH range of 7-9 and a total water dispersible polyurethane resin
at a level of 0-25% by weight.
Component C, reducer base, contains an aqueous solution of; 1) synthetic
sodium lithium magnesium silicate hectorite clay at a level of 0.1-10% by
weight, preferably 0.5-3.0% by weight, 2) a polypropylene glycol at a
level of 0.1-10% by weight and 3) water miscible solvent at a level of
0-25% by weight, 4) a total solids level of 0.1-20% by weight and 5) a
total water level of 50.0-99.9% by weight. Component B, pigmented base,
contains acrylic latex grinding polymer and acrylic latex film forming
vehicle at a level of 5-50%, preferably 15-50%. This level depends on the
pigment in the component. The level of pigment in component B is 0.5-35%
by weight, this level depends on the pigment characteristics also.
Typically, a pigment to binder weight ratio of about 10/100 to 300/100 is
acceptable. The pigments are typically ground using conventional
dispersion equipment such as sand mills, pearl mills, ball mills,
horizonal mills, and vertical mills. Optional wetting agents, surfactants,
and dispersing aids can be employed. This component may also contain a wax
composed of ethylene and/or ethylenically unsaturated monomers alkyl
(meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate,
propyl (meth)acrylate, 2-propyl (meth)acrylate, butyl (meth)acrylate,
2-butyl(meth)acrylate, 2-methylpropyl (meth)acrylate, t-butyl
(meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate,
lauryl (meth)acrylate, octyl (meth)acrylate, decyl (meth)acrylate, stearyl
(meth)acrylate, dicyclopentadienyl (meth)acrylate, and isobornyl
(meth)acrylate; aryl monomers such as styrene, alpha-methyl styrene, vinyl
toluene, t-butyl styrene, benzyl (meth)acrylate, and 2-benzylethyl
(meth)acrylate; hydroxy monomers such as hydroxyethyl (meth)acrylate,
hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate,
sec-hydroxybutyl (meth)acrylate, and hydroxyoctyl (meth)acrylate; acid
functional monomers such as acrylic acid, methacrylic acid, maleic acid,
and itaconic acid. Typically, the particle size of the wax particle in the
final dispersion is 0.5 microns to 50 microns, preferably 1.0 to 20.0
microns. The wax is dispersed by conventional techniques or emulsified in
to the resin system to the desired particle size. The proper amount of the
wax dispersion is then added to the pigmented base. The pH of the
pigmented base can be adjusted using ammonia or any water soluble primary
amines, secondary amines, tertiary amines, polyamines and hydroxyamines,
such as ethanolamine, diethanolamine, triethanolamine, n-methylethanol
amine, N,N diethylethanolamine, N-aminoethanolamine,
N-methyldiethanolamine, monoisopropanolamine, diisopropanolamine,
triisopropanolamine, hydroxyamine, butanolamine, hexanolamine, methyl
diethanolamine, N,N-diethylaminoethylamine, ethylene diamine, diethylene
triamine, diethylene tetraamine, hexamethylene tetramine, triethylamine
and the like. The preferred base is ammonia.
DESCRIPTION OF INVENTION
This invention is directed to a coating composition for a water borne base
coat especially designed for the automotive market. This invention
describes a method for the introduction of metallic flakes into a water
borne coating resulting in a highly superior base coat. The proper metal
fixation is accomplished by the use of a novel rheology control agent
which employs a synthetic sodium lithium magnesium silicate hetorite clay
and a polypropylene glycol. The metallic base coat is broken down into
three bases that are combined just prior to application of the base coat.
The nonmetallic base coat is broken down into two bases that are combined
just prior to application of the base coat.
The invention describes a method for the storage of aluminum flake in an
organic medium with introduction of the flakes directly into the aqueous
environment just prior to application of the coating system. An acrylic
resin with both nonionic and acid functionality has been developed that
allows for this introduction of the aluminum flakes into the aqueous
environment without the neutralization step. This method minimizes the
potential hazard of the aluminum flake reacting with water to form
hydrogen gas during storage.
Component A, aluminum base, is an aluminum slurry in an organic environment
containing an acrylic resin having nonionic and acid functionality. The
aluminum dispersion resin is an acrylic polymer in water-miscible
solvent(s), formed by the free-radical initiated polymerization of
ethylenically unsaturated monomers. A polyether-containing ethylenically
unsaturated monomer is included in the monomer mixture, to give a final
poly(ethylene oxide) level of 1-50% by weight, preferably 5-20% by weight.
The number average molecular weight of the polymer is between 1,000 and
50,000 atomic mass units, its Glass Transition Temperature (Tg) is between
-20.degree. and +50.degree. C. (calculated by the Fox method), its
hydroxyl number is 0 to 50, and its acid number is from 5 to 50 milligrams
of KOH per gram of resin solids. The viscosity of the final polymer is
3,000-10,000 cps with a solids content of 60-70% by weight at 23 C.
Ethylenically unsaturated monomers which can be used for this purpose
include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, 2-propyl (meth)acrylate, butyl
(meth)acrylate, 2-butyl (meth)acrylate, 2-methylpropyl (meth)acrylate,
t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl
(meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl
(meth)acrylate, stearyl (meth)acrylate, dicyclopentadienyl (meth)acrylate,
and isobornyl (meth)acrylate; aryl monomers such as styrene, alpha-methyl
styrene, vinyl toluene, t-butyl styrene, benzyl (meth)acrylate, and
2-benzylethyl (meth)acrylate; hydroxy monomers such as hydroxyethyl
(meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate,
sec-hydroxybutyl (meth)acrylate, and hydroxyoctyl (meth)acrylate; acid
functional monomers such as acrylic acid, methacrylic acid, maleic acid,
and itaconic acid.
Examples of polyether-containing monomers include poly(ethylene glycol)
mono(meth)acrylate (containing 5 to 20 ethylene oxide units), and any
other ethylenically unsaturated monomer that contains polyether units.
The acrylic polymer is prepared in organic solvents that are water
miscible, such as methyl ethyl ketone, acetone, ethanol, methanol,
propanol, butanol, N-methylpyrrolidone, glycols, glycol ethers, glycol
acetates, diethylene glycol ethers, diethylene glycol acetates, propylene
glycol ethers, propylene glycol acetates, dipropylene glycol ethers,
dipropylene glycol acetates, specially preferred are ethylene glycol
propyl ether, ethylene glycol butyl ether, ethylene glycol hexyl ether,
propylene methyl ether, propylene ethyl ether, propylene propyl ether,
propylene butyl ether, propylene hexyl ether, dipropylene methyl ether,
dipropylene ethyl ether, dipropylene propyl ether, methyl ethyl ketone and
dipropylene butyl ether. The acrylic polymer is prepared via normal
solution polymerization techniques. Examples of free-radical initiators
include peroxides, such as benzoyl peroxide, tertiary-butyl peracetate,
tertiary-butyl peroctoate, tertiary-butyl perbenzoate, and ditertiary
butyl peroxide; and 1,1'-azobis(alkyl nitrile)s, such as
,'-azobis(isobutyronitrile), and 1,1'-azobis(cyclohexane carbonitrile).
Optionally, surfactants can also be present during the polymerization at a
level of 0.1-2.0% by weight.
Any commercial aluminum paste available for solvent borne or water borne
applications can be used in the preparation of component A. The amount of
aluminum flake in the component is 4-30% by weight, preferably 23-30% by
weight.
Other nonmetallic and metallic pigments that can be incorporated into this
base include copper, copper alloys, mica, coated metallic foils, plastic
flakes and steel. However, this is not an inclusive list.
Additional organic solvent may be needed to reduce the viscosity of the
acrylic resin. Acceptable solvents must be water miscible such as methyl
ethyl ketone, acetone, ethanol, methanol, propanol, butanol,
N-methylpyrrolidone, glycols, glycol ethers, glycol acetates, diethylene
glycol ethers, diethylene glycol acetates, propylene glycol ethers,
propylene glycol acetates, dipropylene glycol ethers, dipropylene glycol
acetates, specially preferred are ethylene glycol propyl ether, ethylene
glycol butyl ether, ethylene glycol hexyl ether, propylene methyl ether,
propylene ethyl ether, propylene propyl ether, propylene butyl ether,
propylene hexyl ether, dipropylene methyl ether, dipropylene ethyl ether,
dipropylene propyl ether and dipropylene butyl ether. Component A, the
aluminum base, has a total solids level of 25-55% by weight, 5-35% binder
by weight, 35-50% organic solvent by weight and total metallic pigment
level of 4-30% by weight. Additional wetting, anti-settling additives
common to the paint industry may be added.
The preparation of component A, the aluminum base, is critical for the
proper appearance of the aluminum flake in the final coating. The proper
amount of the acrylic resin solution is dissolved into the proper amount
of water miscible organic solvent, such as methyl ethyl ketone, acetone,
ethanol, methanol, propanol, butanol, N-methylpyrrolidone, glycols, glycol
ethers, glycol acetates, diethylene glycol ethers, diethylene glycol
acetates, propylene glycol ethers, propylene glycol acetates, dipropylene
glycol ethers, dipropylene glycol acetates, specially preferred are
ethylene glycol propyl ether, ethylene glycol butyl ether, ethylene glycol
hexyl ether, propylene methyl ether, propylene ethyl ether, propylene
propyl ether, propylene butyl ether, propylene hexyl ether, dipropylene
methyl ether, dipropylene ethyl ether, dipropylene propyl ether and
dipropylene butyl ether. The proper amount of the aluminum paste is
slurred into the above described resin solution. The aluminum slurry must
be stirred until the base is smooth and uniform.
Component B, pigmented base, imparts the coloring effect upon the coating
composition. The resin used for the dispersing of the pigments is an
acrylic latex. Typical properties of this acrylic latex are as follows:
______________________________________
Solids content, % 20-60
pH 7 to 10
Weight per gallon, lbs
8.0 to 9.0
Minimum film formation temperature, C.
0 to 70
Sward hardness 25 to 110
Mechanical stability OK
Glass transitition temperature, C.
10 to 50
Average molecular weight
150,000 to
300,000
Number average molecular weight
30,000 to 60,000
Acid number on solids 5 to 35
Volatile organic solvents, %
0 to 20
Particle size, nm 50 to 150
______________________________________
Especially preferred acrylic lattices are Neocryl A-622, Neocryl A-640,
Neocryl A-6037 sold by ICI Resins, Joncryl J-537, Joncryl J-538 sold by
Johnson Wax, Arolon 860-W-45 sold by NL Industries. The level of this
resin in component C is 15-60% by weight, preferably 20-40% by weight. The
organic, inorganic pigments and/or dyestuffs are ground with this resin
employing standard techniques. Examples of dispersing equipment are ball
mills, pebble mills, pearl mills, horizontal mills, and vertical mills.
Examples of pigments and dyestuffs but not limited to are titanium
dioxide, graphite, carbon black, zinc oxide, cadmium sulfide, chromium
oxide, zinc sulfide, zinc chromate, strontium chromate, barium chromate,
lead chromate lead cyanamide, lead silico chromate, chromium oxide, zinc
sulfide, yellow nickel titanium, yellow chromium titanium, red iron oxide,
transparent red iron oxide, transparent yellow oxide, black iron oxide,
ultramarine blue, phthalocyanine complexes, amaranth, quinacridones, and
halogenated thioindigo pigments. The level of pigment/dyestuff in
component C is 0.0-45.0% by weight, typically 0-25%. This component may
also contain a wax composed of ethylene and/or ethylenically unsaturated
monomers alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, 2-propyl (meth)acrylate, butyl
(meth)acrylate, 2-butyl(meth)acrylate, 2-methylpropyl (meth)acrylate,
t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl
(meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, decyl
(meth)acrylate, stearyl (meth)acrylate, dicyclopentadienyl (meth)acrylate,
and isobornyl (meth)acrylate; aryl monomers such as styrene, alpha-methyl
styrene, vinyl toluene, t-butyl styrene, benzyl (meth)acrylate, and
2-benzylethyl (meth)acrylate; hydroxy monomers such as hydroxyethyl
(meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate,
sec-hydroxybutyl (meth)acrylate, and hydroxyoctyl (meth)acrylate; acid
functional monomers such as acrylic acid, methacrylic acid, maleic acid,
and itaconic acid. Typically, the particle size of the wax particle in the
final dispersion is 0.5 micron to 50 micron, preferably 1.0 micron to 20.0
micron. Typical properties of this wax are as follows:
______________________________________
Acid Number (mg KOH/g) 0-50
Hardness, dmm (ASTM D-5)
<2.0
Mettler Drop Point, C (ASTM D-3104)
100-150
Particle Size, micron 0.5-10.0
Hydroxy Number 0-50
______________________________________
Typically, the wax is dispersed by conventional techniques in to the resin
system to the desired particle size or be prepared by emulsion techniques.
The proper amount of the wax dispersion is then added to the pigmented
base. This component may also contain other conventional paint additives
such as dispersing aids, anti-settling aids, wetting aids, thickening
agents, extenders, plasticizers, stabilizers, light stabilizers,
antifoams, defoamers and catalysts singly or a multitude of them at the
conventional levels. Also present in this component is a water miscible
solvent such as methyl ethyl ketone, acetone, ethanol, methanol, propanol,
butanol, N-methylpyrrolidone, glycols, glycol ethers, glycol acetates,
diethylene glycol ethers, diethylene glycol acetates, propylene glycol
ethers, propylene glycol acetates, dipropylene glycol ethers, dipropylene
glycol acetates, specially preferred are ethylene glycol propyl ether,
ethylene glycol butyl ether, ethylene glycol hexyl ether, propylene methyl
ether, propylene ethyl ether, propylene propyl ether, propylene butyl
ether, propylene hexyl ether, dipropylene methyl ether, dipropylene ethyl
ether, dipropylene propyl ether and dipropylene butyl ether at a level of
0-25% by weight, preferably 0-12% by weight. Examples of water reducible
polyurethanes are NeoRez R-960, R-966, R-967, R-9637 manufactured by ICI
Resins and Spensol L51 and L53 manufactured by NL Industries. Component B,
the pigmented base, has a total solids level of 5-60% by weight, a total
pigment level of 0.0-45% by weight, a total organic solvent level of 0-25%
by weight, a total binder of 20-60% by weight, a total wax level of 0-20%
by weight, a total polyurethane level of 0-25% by weight, a total water
level of 40-95% by weight and a pH range of 7-9. The pH of the base can be
adjusted using ammonia or other water soluble primary amines, secondary
amines, tertiary amines, polyamines and hydroxyamines, such as
ethanolamine, diethanolamine, triethanolamine, n-methylethanol amine, N,N
diethylethanolamine, N-aminoethanolamine, N-methyldiethanolamine,
monoisopropanolamine, diisopropanolamine, triisopropanolamine,
hydroxyamine, butanolamine, hexanolamine, methyl diethanolamine,
N,N-diethylaminoethylamine, ethylene diamine, diethylene triamine,
diethylene tetraamine, hexamethylene tetramine, triethylamine and the
like.
Component C, reducer base, is an aqueous solution containing a dispersion
of synthetic sodium lithium magnesium silicate hectorite clay and a
polypropylene glycol. Addition of a polypropylene glycol to the hectorite
clay results in a low viscosity dispersion. This low viscosity dispersion
of the hectorite clay allows for easy incorporation of the dispersion into
the paint composition. The polypropylene glycol also allows the coating to
be sprayed wetter onto the substrate. The typical properties of the
synthetic sodium lithium magnesium silicate clay are as follows:
______________________________________
Solids Content, %
95-100
Typical Analysis
SiO2 50-65
MgO 25-35
Li2O 0.1-1.5
Na2O 1.5-3.5
3.0-12.0
Appearance White free
flowing powder
Particle Size <2% greater than 250 microns
Surface Area, m2g
370 s
______________________________________
Especially preferred synthetic sodium lithium magnesium silicate hectorite
clay is Laponite RD, available from Laporte, Inc.
This hectorite clay is present in this component at a level of 0.1-10% by
weight, preferably 0.5-3.0% by weight. This component also contains a
polypropylene glycol at a level of 0.1-10% by weight. The molecular weight
range of the polypropylene glycol is 435 to 3900. The hectorite clay can
be dispersed in the aqueous medium by Cowles or agitation. A water
miscible solvent may also be present in this component such as methyl
ethyl ketone, acetone, ethanol, methanol, propanol, butanol,
N-methylpyrolidone, glycols, glycol ethers, glycol acetates, diethylene
glycol ethers, diethylene glycol acetates, propylene glycol ethers,
propylene glycol acetates, dipropylene glycol ethers, dipropylene glycol
acetates, specially preferred are ethylene glycol propyl ether, ethylene
glycol butyl ether, ethylene glycol hexyl ether, propylene methyl ether,
propylene ethyl ether, propylene propyl ether, propylene butyl ether,
propylene hexyl ether, dipropylene methyl ether, dipropylene ethyl ether,
dipropylene propyl ether and dipropylene butyl ether at a level of 0-25%
by weight, preferably 0-12% by weight.
Other water reducible resin may be added to the coating to improve certain
film properties such as aqueous one-component aliphatic polyurethane
dispersions, aromatic polyurethane dispersions, polyesters, and alkyds.
Addition of an acrylic acid and/or polyurethane based thickeners known to
the art may also be added to achieve desired properties. The incorporation
of metal oxides such as zinc oxide may also improve the humidity
resistance of the final film.
Additional anionic and nonionic surfactants can be added to the paint
composition to increase wetting of the substrate by the coating such as
FC-120, FC-430 sold by 3M, Surfynol 104, Surfynol 440 sold by Air
Products, Triton X-100 sold by Rohm and Haas, Troysol LAC sold by Troy
Chemical Company, Aerosol OT's sold by American Cyanamid including the
salts of dialkyl sulfosuccinates and Igepal's sold by GAF including the
ethoxylated alkyl phenols.
This base coat composition exhibits a very high viscosity at low shear rate
while having a low viscosity at high shear rates. This phenomenon results
in the outstanding metal effect this coating composition possesses. The
efflux time of the coating through a #4 Ford cup is 15 to 30 seconds at 23
C.
The coating composition can be applied using conventional spray equipment
or high volume low pressure spray equipment resulting in a high quality
finish. Other modes of application are roller coating, brushing,
sprinkling, flow coating, dipping, electrostatic spraying, or
electrophoresis. Suitable substrates may be made of wood, metal, and
synthetic material. After a flash off time of 15 to 45 minutes, a
transparent top coat can be applied over this base coat. The preferred
transparent clear coat is two component, based on acrylic and/or polyester
resins cured with polyisocyanates. Other examples of cured transparent
clear coats are acrylic and/or polyester resins cured with silanes,
acrylic and/or polyester acid cured epoxy coatings, and acrylic and/or
polyester resins cured with aminoplast resins, however, this is not an
inclusive list.
PREFERRED EMBODIMENTS OF INVENTION
The following examples illustrate the invention without limiting the scope
thereof.
EXAMPLE 1
Base Coat Preparation
Approximately 134 grams of Propylene glycol monopropyl ether is combined
with 5 grams of Methyl Ethyl Ketone in a one-liter distillation flask,
fitted with a water-cooled condenser, under a Nitrogen blanket. The
mixture is brought to reflux (.about.140.degree. C.), the Nitrogen flow
reduced to a minimum, and 454 grams of a mixture of ,.beta.-ethylenically
unsaturated monomers is pumped into the flask over two hours. The monomer
mixture consists of Methyl Methacrylate--7.2%, Styrene--18.8%. n-Butyl
Methacrylate--48.1%, Acrylic Acid--1.7%, 2-Ethylhexyl Acrylate--2.4%,
alpha-Methyl Styrene--1.7%, and Polyethylene Glycol Monomethacrylate
(containing 10 Ethylene oxide units)--19.9%. While the monomers are being
pumped into the reaction flask, a mixture of 11 grams of free-radical
initiator (t-Butyl Perbenzoate) and 50 grams solvent (propylene glycol
monopropyl ether) is simultaneously fed into the flask over two hours.
After adding all the monomers, solvent, and initiator (and flushing the
pumps and feed lines with propylene glycol monopropyl ether), the reaction
is held at reflux. After thirty minutes at reflux, a mixture of 1.7 grams
of initiator and 35 grams of solvent (propylene glycol monopropyl ether)
is pumped into the reaction flask over ten minutes. After adding the
initiator and solvent mixture, the reaction is held at reflux. After one
to two hours at reflux, the reaction is cooled and filtered into a lined
metal can. The viscosity of this polymer is between 6,000 and 8,000 cps at
63.4% non-volatile by weight, measured at 25 .degree. C., and its acid
number is from 14 to 16 milligrams of KOH per gram of resin solids.
PREPARATION OF COMPONENT A--ALUMINUM BASE
A commerical solvent borne aluminum paste, 60.0 g, was added to 60.0 g of
butoxyethanol. The mixture was stirred until a homogeneous dispersion was
produced. To this dispersion, 30.0 g, of the resin described above was
added to the dispersion and the entire mixture stirred until a smooth,
uniform slurry was produced. This aluminum base contains 39% volatile
organic solvent by weight, a soldis level of 61.0% by weight, a binder
level of 13% by weight and an aluminum flake level of 26.0% by weight.
PREPARATION OF COMPONENT B--PIGMENTED BASE
The following pigment slurry was prepared, 12.2 g of NeoCryl A-6037, 14.8 g
of NeoCryl A-640, 0.3 g of 30% aqueous ammonia, 3.2 g of Perrindo Maroon
R-6424 manufactured by Mobay Corporation, 0.1 g of a defoamer and 0.05 g
of Surfynol 104BC manufactured by Air Products. The above mixture were
mixed together and predispersed using a Cowles blade. The mixture was then
ground on a sand mill until the desired particle size was achieved. A let
down solution containing 29.5 g of NeoCryl A-622, 2.6 g of butoxyethanol,
1.3 g of deionized water and 0.03 g of 1% aqueous solution of FC-120 was
added to the grind portion under agitation. An unpigmented base can be
prepared using the procedure above with the elimination of the Perrindo
Maroon R-6424 pigment. A wax dispersion was prepared by grinding 50.0 g of
a wax, 50.0 g of unpigmented resin solution, 50.0 g of deionized water and
50.0 g of butoxyethanol. This paste was ground to the desired particle
size using conventional techniques. To the pigmented and unpigmented bases
described above, 6.0 g of this wax dispersion was added with stirring.
Also added to the pigmented and unpigmented bases describee above was 16.0
g of NeoRez R-9637 manufactured by ICI Resins. The resulting pigmented
base had a pH of 8.4, a solids level of 38.1% by weight, a volatile
organic level of 10.5% by weight, a binder level of 34.2% by weight, a
pigment level of 4.3% by weight and a water level of 51.4% by weight. The
unpigmented base has a solid level of 35.4% by weight, volatile organic
level of 9.5% by weight, a water level of 55.1% by weight and a pH of 8.5.
PREPARATION OF COMPONENT C--REDUCER BASE
To 1953.2 g of deionized water, 31.3 g of Laponite RD manufactured by
Laporte Industries and 10.7 g of Pluracol P1010 manufactured by BASF
Corporation was added. The resulting solution was then agitated for one
hour until the Laponite RD was completely dispersed. To this solution was
added 1953.2 g of deionized water. The resulting mixture had a Laponite RD
level of 0.79% by weight and a polypropylene glycol level of 0.27% by
weight.
EXAMPLE 2
Preparation of a Water Borne Red Metallic Base Coat
______________________________________
Component Parts by Weight
______________________________________
Component A 16.0
Aluminum Base
Component B 54.0
Pigmented Base
Component C 85.0
Reducer Base
______________________________________
The above formula was used to prepare a red metallic base coat. The order
of addition is that listed. After each introduction of a component, the
entire solution was stirred. The base coat was sprayed on panels primed
with an epoxy primer. The base coat was sprayed on the substrate using
conventional spray equipment until hiding was achieved. The base coat was
allowed to flash for 30 minutes and then clear coated with a transparent
coating based on isocyanate technology. The final properties of the base
coat after coating with a conventual polyurethane clear coat are listed
below, including appearance ratings.
______________________________________
Properties of the Red Metallic Base Coat and
Base Coat, Clear Coat System
Property Value
______________________________________
Water 72.5%
Volatile Organic 7.4%
Pigment 2.4%
Nonvolatile 20.1%
Binder 10.8%
Weight per Gallon (lbs/gal)
8.4
VOC (lbs/gal) 2.4
Gloss, 20 deg 90
DOI 84
Adhesion good
Film Thickness (mil)
0.34
Humidity good
Water Spray excell.
Metal Control excell.
______________________________________
EXAMPLE 3
Preparation of a Water Borne Silver Metallic Base Coat
______________________________________
Component A 16.0 g
Aluminum Base
Component B 54.0 g
Unpigmented Base
Component C 85.0 g
Reducer Base
______________________________________
The above formula was used to prepare a silver metallic base coat. The
order of addition is that listed. After each introduction of a component,
the entire solution was stirred. The base coat was sprayed on panels
primed with an epoxy primer. The base coat was sprayed on the substrate
using conventional spray equipment until hiding was achieved. The base
coat was allowed to flash for 30 minutes and then clear coated with a
transparent coating based on isocyanate technology. The final properties
of the base coat after coating with a conventional polyurethane clear coat
are listed below, including appearance ratings.
Properties of the Silver Metallic Base Coat and Base Coat, Clear Coat
System
______________________________________
Property Value
______________________________________
Water 73.1%
Volatile Organic 7.7%
Pigment 2.7%
Nonvolatile 19.2%
Binder 11.2%
Weight/Gallon (lbs/gal)
8.4
VOC (lbs/gal) 2.6
Gloss, 20 89
DOI 90
Adhesion good
Film Thickness (mil)
0.53
Humidity good
Water Spray excell.
Metal Control excell.
______________________________________
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